


Just Sibling Things

by Piriluk (orphan_account)



Category: Vocaloid
Genre: Angst and Humor, Brother/Sister Incest, Eventual Romance, Eventual Sex, Eventual Smut, F/M, Humor, Implied/Referenced Incest, Incest, Light Angst, Romance, Sexual Content, Sexual Humor, Sexual Tension, Sibling Incest, Smut
Language: English
Status: Completed
Published: 2015-12-26
Updated: 2015-12-26
Packaged: 2018-05-09 11:23:03
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 8,830
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5538032
Author URL: https://archiveofourown.org/users/orphan_account/pseuds/Piriluk
Summary: <blockquote class="userstuff">
              <p>When family wants you to have grandchildren, but in all honesty, you've been too busy screwing your twin sister in secret to care about legal relationships. #justsiblingthings. ONESHOT.</p>
            </blockquote>





	Just Sibling Things

**Just Sibling Things**

When family wants you to have grandchildren, but in all honesty, you've been too busy screwing your twin sister in secret to care about legal relationships. #justsiblingthings

.

.

.

_five_

"What do you mean you don't feel well?" Lily asked, not even casting a side glance at the small girl who stood at the foot of her desk chair. "Rin, don't be silly. I know you're just making it up to avoid going to bed - don't think Mummy is fooled."

Her daughter whimpered, clutching at the hem of her shirt. "I really mean it," she said. "I really don't feel well. My stomach is sore…"

The woman looked down at the child, as if her face would show visible signs of the self-proclaimed unwellness. "You don't _look_ sick," she analysed. Rin pouted. "Come on, go hop into bed. Len is waiting for you."

She nodded at the boy standing awkwardly in the doorway of the hall, who'd been watching them talk for the past few minutes. He absentmindedly had one hand in his mouth, sucking on it fervently as if he hadn't eaten dinner. The other hand clutched a faded, dirty blanket he insisted on carrying everywhere.

He was kind of a… unique child.

Lily sighed at the pair. "Go on. I'll be there in a minute."

Rin, unhappy her complaints went unheard, pushed past Len and trudged upstairs. Her brother followed after her, tripping over 'blanky' several times before figuring that lifting it off the ground would make life easier (and indeed, it did).

"My stomach hurts so much," the girl whined as she climbed up the ladder to the top bunk. "Does your stomach hurt, Len?"

Her twin thought for a moment. "Not really," he admitted, sliding under the sheets of his bed. "Maybe you need to do a poo? I feel better always after doing a poo."

"Poo! I don't need to poo."

"Are you _sure?"_

Instead of answering the question, Rin promptly burst into tears instead.

"No, Rin! Don't cry! I wasn't being a meanie," Len blurted out, panicking. He didn't want to get in trouble for upsetting her, because then he'd probably get his bed taken away, or something. She always liked to fake cry because Len stole her treats, so she got more and he had his treat taken from him as a punishment.

When he didn't hear a reply come from his sister, he sat up in his bed and peered up at the top bunk. "Rin?"

For a moment, she didn't answer, but then her red, tear-stained face popped over the side of the mattress. "Len," she choked out. "I really, _really_ feel si—"

Before the girl could finish her sentence, a stream of warm, putrid-smelling liquid shot out from her mouth, splashing down onto her younger twin's face. Len hardly had time to react - one moment she was talking, the next his hair and shirt was decorated with chunks of dinner.

He began to cry loudly - loud enough to hurry his mother into the bedroom.

"Oh my God," she gasped upon seeing the mess she'd walked into. Both the twins were in tears and vomit.

…She regret not listening to the girl beforehand.

.

.

.

_seven_

It was that age when they were becoming more self-aware, inquisitive, and a little more independent.

Their parents agreed it was maybe a good time to move into a larger house, where the twins could have rooms of their own. The idea was initially great - their mother and father both expected their children to be ecstatic about having separate rooms to decorate to their liking - but that was, unfortunately, not the case.

On the first night, Rin wailed the house down to ashes upon realising she was to sleep in the room adjacent to Len's. The boy noticed the absence of their bunkbed beforehand, but never really thought much of it. Still, he wondered whether it was really necessary for his sister to cry so much. It wasn't like they would never be able to see each other again.

Nevertheless, the female did what she did best - threw a tantrum, screamed and whined all night to get her way.

"God, Rin, I thought you'd be _happy_ about this," her mother grumbled as she tried to coax the girl to bed.

Rin rolled across the ground and cried obnoxiously as Lily tried to pick her up to tuck her into bed. Len observed with amusement from his room's doorway.

"No! I want to sleep with Len! I want to sleep with Len!" his sister yelled, flailing in her mother's arms, attempting to wriggle her way out of her arms.

His dad swooped in, just coming home from work. He followed Len's gaze. "You gonna do this too?" he asked the boy, to which he shook his head, knowing not to get on the bad side of his father.

Leon sighed, closing his eyes.

"What's this I'm hearing?" he boomed, a sudden change of attitude, storming into Rin's room to scope out the scene. Immediately, the young girl fell silent, paling at the sight of her father. "Rin Kagamine, you'll do as your mother tells you, or you're getting grounded for a week."

Len couldn't help but snicker behind his hand on seeing his sister obediently climb under the covers of her bed. He found it hard to believe she could go from defiant to an innocent angel in just a second, but that was the kind of effect their dad had on her. It was funny.

She didn't budge from under the covers, too terrified, which meant play time was officially over. He skulked off to his room and climbed into bed, and waited patiently for his parents to tuck him in.

He'd long drifted off to sleep when he felt someone lightly shaking him awake.

It took no less than a second for him to guess who it was: Rin.

"Len? Are you awake?" her small voice asked.

"I am now," he mumbled into his pillow.

She hesitated, hands still resting on his shoulder. "C-can I please sleep with you? I'm scared…"

Len sighed, rolling over to look at her. Her tiny, pale face stared back at him, illuminated slightly by his nightlight. She blinked her big blue eyes, giving her best puppy-dog look. "Mum and Dad will get angry at you, you know," he pointed out, though he knew she'd won him over already.

Rin shook her head. "No they won't. I'll sneak back into bed before they find us. Promise."

He paused, as if mulling heavily over it, before nodding his head and peeling his covers back to let her in. "Okay."

A victorious smile stretched across her lips and she crawled under the sheets, snuggling up against her brother's body for warmth.

Len draped an arm over her shoulders and thought to himself, _This is better, anyway_.

.

.

.

_eleven_

They'd grown apart with age - though he always had a soft spot for his sister. Somehow.

Otherwise, he thought she was just downright bratty and annoying. She never shut up. She cared too much about what others thought of her. She was trying too hard to be older than what she was - and she loved to rub him up the wrong way.

God dammit.

Rin stopped sneaking into his room around a year ago. When he'd questioned her about it, she'd responded curtly, "Well, you know, _Miku_ doesn't sneak into her brother's room. She thinks that's _weird_."

Miku was Rin's 'bestie', apparently, although they fought more than they ever could agree - honestly.

So, yeah. Len was a little hurt about it, admittedly. _He_ wasn't weird, was he? He didn't mind it when Rin snuck into his room - after all, _she_ was the one who started it, anyway.

Well, whatever.

Apparently anything to do with him nowadays was 'weird'. He just didn't understand girls. _They_ were the weird ones.

One evening after dinner, he and Rin were assigned to washing the dishes. He would clean the dishes, and his sister would dry them and put them away. She would always complain about why they didn't use the dishwasher instead, and no matter how many times their parents would have to explain it to her, she just didn't understand the phrase, 'it saves energy'.

Everytime she would throw a fit about it, and everytime she would be sent to her room as punishment, leaving Len to have to do all the work himself. Of course, tonight, their parents finally cracked onto her sneaky tactic, instead forcing her to do it.

Rin made sure she let everyone know how _unhappy_ she was having to do a basic chore that Len did every other week by himself without her help. She'd become so _sassy_ ever since she'd started hanging out with Miku. Soon she'd be trying to move in with her family, considering she'd so much as kiss Miku's parents feet whenever they brought Miku over on the weekends for playdates.

After grumbling for several minutes about having to do what she was told, she changed the subject to boys as if Len would have an interest the subject. That was unfortunately not the case.

Nevertheless, she told him, "Miku's brother is _so hot_."

"Miku has a brother?" Len asked.

"Uh, yeah. He's in junior high. He's got really nice abs."

Len wanted ask what abs were, but he had a feeling Rin would probably make fun of him instead of answering his question. "Junior high? Uh, ew."

Rin gave him a look as he'd insulted her face. " _Excuse_ me. What's 'ew' about that? He's older and much more mature than stupid boys like _you_."

"My reason exactly. He's _old_. He'll die before you."

"That's incredibly morbid of you, Len."

"Um, what?"

She rolled her eyes, muttering the word, _idiot_.

He frowned to himself. "Well, I'm more mature than other guys. Everyone says that I am."

"That's just because no one wants to be your friend since you're such a loser. All the adults know that but don't want to tell you, so they say you're just too mature for everyone instead."

Len blinked, feeling his skin go warm. That was… _mean_. Well, that was more than mean. He felt humiliated tears prick his eyes, but he swallowed them away. "Well," he said in the most even voice he could muster. "If I were him, I wouldn't be interested in girls like you, because you're so selfish. Plus, he's got a better choice of _women_ in junior high, anyway."

Rin stopped, eyes narrowing. Her cheeks went a brilliant shade of cherry red, right through to her hairline. He'd never seen her turn this colour before - _ever_. "That's not true!" she cried, slamming down the cup she was in the middle of drying. He flinched, expecting the glass to shatter, but somehow it didn't. "You take that back, you twerp! I can't believe you said that!"

"Why should I take that back? You take back what you said first!" he exclaimed.

"It was the truth! You're a _loser!_ This is why no one at school likes you!"

"Well, I—"

"What's all this ruckus I hear?" a booming voice interrupted, and their father appeared in the doorway of the kitchen. The twins straightened, snapping their mouths shut. "Why can't you two, for just _one night_ , agree to do the dishes in peace?! What's there so important to shout about in the kitchen?!"

Rin jabbed a finger accusingly at Len. "He started it!"

"No I did not!" Len defended. "She was the one who said I was a loser first!"

"That's because you _are!_ "

"No I'm _not!_ "

"That's it! Both of you, go to your rooms!" Leon snapped, pointing them off in the direction of the stairs. "Go on! Your mother will be up there soon with the _sorry shirt_."

Immediately, the twins groaned. The dreaded _sorry shirt_ \- in which, they were forced to wear a shirt that fit the two of them at the same time until one another could apologise properly. Len _despised_ it, mostly because Rin would take charge of them and drag him everywhere and push him into walls.

Why did he get the Grinch, of all people, as a twin sister? He honestly thought sometimes that a twin brother would be better.

"Ugh, I'm going to miss out on emailing Miku and Luka tonight, thanks to _you_ ," Rin spat over her shoulder before disappearing into her room.

Len frowned to himself. Well, he wouldn't be missing much. _Because you have no friends_ , a voice that sounded an awful lot like his sister's said in his mind. Was it true? Did he really have no friends? He was sort of friends with Kaito - when it suit him, anyway.

He guessed it was true. And it really kind of hurt. A lot, maybe.

.

.

.

_thirteen_

"So, I heard Miku asked you out yesterday," a voice said, and without turning his head, he knew it was Rin.

Len shrugged his shoulders, scanning over his homework. This was the first time she'd talked to him in maybe, er, a week or so? The girl was erratic like that. Sometimes she'd be nice - other times, he was dead to her, in all ways physical and mental. "Yeah. She did."

"I see." Rin leant up against the frame of his door and folded her arms over her chest.

He finally looked at her, and she raised an eyebrow back at him, a scowl touching just at the edges of her expression. "What? Did you two have another fight, or something?"

"'Another' fight?" his sister quoted. "We stopped being friends like three months ago." She said it like he should've known that already.

Len swallowed, looking back at his homework. "Oh. That's sad." Not really. He was waiting for it to happen, actually. "Why's that?"

"She kept bugging me to hook you up with her," she answered.

"What's… wrong with that, exactly? To, you know, end a friendship for?"

"It's gross. And there were other things, of course."

He looked over at her, as if expecting her to explain a little more, but she had her lips pressed together in a thin line, clearly not letting her reasoning get any deeper. "Gross. Okay. That's nice."

Rin rolled her eyes and ignored his statement. "I didn't come here to talk about this. I came to hear about your answer. What'd you say back?"

Len shrugged again. "I just said I wasn't interested in dating."

"Oh. Alright."

It was his turn to raise an eyebrow. "Why'd you want to know?"

She paused, mulling over a response. She held his gaze, keeping a neutral expression, as if challenging him, almost. "Huh," she said. "Just 'cause. I didn't want you to date her, so it's good you said no."

"Well, why? Because you're not friends anymore?"

Rin tucked a strand of hair behind her ear. "Well, partially that. But also because you're mine."

Len thought he'd misheard her. Terribly. He blinked. "I'm what?"

Her lips twitched into a smirk. "Nothing."

Before he could question her anymore about her strange answer, she left, locking herself away in her room.

_As if_ his sister could get any _weirder_ , for the matter - and then she just dropped that bombshell on him. He hardly knew how to take her. Seriously.

.

.

.

_fifteen_

It was all good and well until Rin walked in on him doing - uh, _that_.

You know.

Need he say more?

Erm, well, _anyway_ \- he'd managed to stealthily throw a sheet over his lower half, but that still didn't fix the problem considering that she had _still_ managed to see him touching his wanger, mid-moan, with no sort of dignity at all. He _swore_ he locked the door, dammit.

Len was on his way to the volcanic explosion, and then _she_ \- Rin - of _all_ people, waltzed into his room, about to launch into some spur-of-the-moment conversation, only to be stopped in her tracks by his tomato face and pulsating boner.

Thank goodness she walked in _then_ and not a few moments later. It would've been a lot more… interesting, to put it safely.

"Oh, don't look so _beside_ yourself, Len," Rin scoffed after recovering from the initial shock of seeing her brother jacking off as if preparing to launch himself to the moon. "I've seen plenty of penises before. Yours certainly isn't the first. Or the last." She laughed heartily, before eyeing his crotch area, now hidden away under his bedsheets.

"C-can we not?" came his flustered reply. "Wait - _when have you seen other penises?_ "

His sister just smirked. "Places," she told him simply. "And then there's you. Hanging it out for all the world to see. Good on you, Len."

"Well, maybe you should learn to _knock_ ," he argued, moving his hands conscientiously to his crotch. He hated how she kept - you know, _looking_ at it.

Rin blew a raspberry. "Maybe you should find some decency. Gosh." She shook her head, then changed the subject like it was hardly anything big. "Anyway, I was _just_ coming in to ask if you wanted to see a movie this weekend. Then again, perhaps you'll be a little… _busy_."

"Can you please stop looking at my penis?!" Len cried, more than just mortified.

"How can I stop when it's just _right there?_ " she said, eyes flicking momentarily to his face. "Penises are such mysterious creatures of the deep. I'm drawn to them like mermaids. And _puh-lease_ , I've seen your dick multiple times before, you know. This isn't exactly shocking, considering you've had one since you were like, in the same womb as me."

He inhaled sharply. "Please, please get out of my room."

Rin flicked her hair black and sighed. "Jeez. Alright, you prude. I just want to know - are you coming to the movies, or are you _coming_ to the movies?"

"Jesus Christ, Rin, whatever, I'll go to the movies - _now get out_."

.

.

.

_sixteen_

"A boyfriend?" Len echoed.

"Yeah," Rin agreed.

He raised an eyebrow at the girl across the living room. "Well. Okay. And your point is?"

She shifted her weight, leaning against the back of one of the couches. She gave him a simple shrug of the shoulders. "You know."

"No, Rin," he said with a sigh. "I _don't_ know."

Lately, his sister had been awfully _social_ with him. He wasn't sure whether it had something to do with the penis incident a while ago, or something else - considering just over a year or so ago she would find every way imaginable to get him into trouble for something _she'd_ done. Her pathetic insults were starting to become a thing of the past, too.

And now, Rin had come to him asking for 'help'. With what, exactly? Well, a boy of course: her supposed 'boyfriend' who she managed to find, somehow, over the summer break. It was strange considering he rarely ever saw her leave the house, but whatever. Rin was just strange in general.

She licked her lips in thought. "I just need you to help me out with what boys _like_ , that's all. It's simple, really."

"Is that so," Len murmured. "It depends on what you're asking. Men, collectively, do not all think the same way as I do."

"True," Rin mused. "For all I know, you could be gay."

"Rin, how could I be gay when there's clear evidence in my internet history that females are the only thing of interest?" He paused. "Wait. Don't you _dare_ look into my history."

His sister gave him a suspicious grin, as if considering the thought.

He cursed himself mentally.

"Alright. Just - you've never _dated_ anyone before, is all," she pointed out. "And I mean, you've got a pretty good relationship with that hand of yours."

Len narrowed his eyes. "What else am I supposed to use? Kitchen utensils? Pillows? Trust me, I've tried. You can't just rent vaginas."

"Yes, you can. They're called prostitutes, Len."

"—legally," he corrected. "Let's not talk about this again. It's really weird how you keep bringing up the fact I masturbate, Rin. Literally, what guy _doesn't?_ " He waited for an answer, and took her silence a reason to continue, "Basically, every guy does. So why do you have a problem with _me_ doing it? There's probably a likely chance that boyfriend of yours has came all over himself thinking of riding you."

"Oh, don't mention that," Rin said with a mischievous glint in her eyes. "You might just get me excited."

Len put his head in his hands. "Please no. Anything but that."

If anything, her grin intensified. Sadist. "Okay, so… give me tips. What do guys like girls to do when they kiss?"

"Um. I don't know. Try asking a person who's kissed someone else before?"

Rin glanced over her shoulder, as if checking her surroundings for something. Whatever she was looking for must've not been there, because she exhaled, almost like she was relieved, and stepped forward towards her brother.

He pressed his lips together, watching her actions. _Hmm. Suspicious,_ he studied. She was up to something - he had the feeling.

She walked over to sit on the lounge facing his. "Wait, you haven't even _kissed_ someone before?" she echoed, leaning forward.

Len sat up. "Um, no, I haven't. Have _you?_ "

Rin blinked. "Well, no."

"Then why are you acting so shocked?"

She shook her head, dismissing the question. "Well, whatever. Did you want to do some research, then?"

Len eyed her. "Research? What, on Google? You can do that without me. I _know_ you know how to use a computer, for sure."

Rin snorted. "No, you big doofus. I meant…" She leant towards him again, puckering her lips.

Oh no. He did _not_ have a good feeling about this.

"You're trying to prank me, aren't you?" he whispered, as if cameras were on him at that moment, recording his every move.

"Oh my _God_ , Len," his sister breathed, sounding exasperated. "No. I'm being serious. We've kissed before. It's not like it's some foreign ritual. We just lean forward, have a quick _mwuah_ , and there - research. You relay to me what you liked about my kissing- or, alternatively, what you _didn't_ like."

"Okay, for one," Len began, holding up a finger. "I already know what I don't like. A) You're my sister. B) You're my _sister_. Why don't you go ask one of your guy friends to practice on? Why _me?_ I'm the worst choice out of the lot."

Rin folded her arms over her chest. "Because you're _here_ , readily available, wasting your life away," she stated. "Besides, you could probably do with some practice yourself."

He frowned. "Gee, thanks."

"Well, we weren't all born _winners_ , Lennie."

Len opened his mouth, then closed it again, much like a goldfish. "Still. I'm not going to kiss you. That's just weird. And gross. And borderline illegal. What happens if Mum or Dad saw us? We'd be dead. They'd send one of us to another country."

"Mum and Dad aren't around," she told him. "And anyway, if they did see us, I'd just tell them I fell."

"Uh, _no_ ; you'd tell them I forced myself onto you and then I would be the one being sent to Europe or something."

"Aw, c'mon Lenners. Live on the edge a little. Be a little less nerd and a little more… word."

"That made absolutely _no_ sense."

"But it was a pretty good rhyme, right? I'm planning on being a rapper when I'm 60. I'll rap in my grave and entertain all the dead people. It'll be great." She stopped to give her brother a sweet smile. " _Please?_ "

For a moment, Len was hypnotised by the smile - before he realised what she was doing, of course. "Goodness, no," he said hastily. "Why don't you tell your boyfriend you've never kissed before and that way you can practice on him even more?"

"Nuh-uh." Rin placed her hands on either of his shoulders, holding him still. She kept her eyes level with her gaze. "Please, Len? For me?" she begged in a gentle voice. "I'll buy you really expensive shoes for Christmas—"

"I don't need sho—" Before he could finish his sentence, his sister had placed her lips on his own.

First there was panic and the sudden urge to throw her away from him a bit like a rag doll, before some sort of demon possessed him and said, _hey, her lips are really nice_ \- and they really _were_. They were soft and sweet, much like how they'd always looked, and warm and just that little bit moist -

Dear God, what on Earth was he thinking? This was his _sister._ His goddamned _sister._ Technically he was kissing a bit of a muddled version of himself, and that thought alone was enough to make any pleasure die like the population after an epidemic.

He finally grabbed hold of his senses and pushed Rin away for the sake of his and her sanity, their lips parting with a very guilt-ridden smack. His sister blinked, as if in a daze, lips looking just as alluring as they'd felt - _stop that_.

Len stood from the lounge and moved away, dry-heaving into his hand. "Christ almighty," he hissed, wiping his mouth furiously on his sleeve as if the kiss would give him herpes - or worse, _cooties_.

"My kissing wasn't _that_ bad, was it?" Rin cried, following after him as he searched the house for somewhere to purge his mouth of the great sin he'd just committed. "I brushed my teeth and everything!"

He stopped in the kitchen, opening the cupboards hoping to find something like methylated spirits to drown his sorrows in. Unfortunately, his wish was not granted - but they _did_ have dishwashing detergent, which was close enough, he supposed. He fetched the bottle from the shelf and popped the lid, ready to take a (very painful) swig, but a hand reached out and snatched it from his grasp.

"Hey, no need to be a drama queen!" his sister exclaimed, looking flushed, and the slightest bit offended. "Okay, so clearly my kissing needs work, but _seriously_ Len, you don't have to be mean—"

"Mean?!" Len repeated. "You just kissed me! You - my _sister_ \- of all people!"

"So?!" Rin yelled, an intense shade of crimson. "Nothing happened! Jeez, it's not the end of the world!"

He took a moment to breathe. She was right. Nothing happened.

Oh great. And now he was looking at her _lips_ again. Freaking hell. He closed his eyes.

"How was it, really?" she asked, volume returning to normal. "Besides the fact that we're related, as you have clearly established at least a trillion times within the past five minutes."

_Well, that's a bit of an exaggeration,_ he commented in his mind. "It was fine. You're fine. If you did what you did with me, your boyfriend won't even know you're new to it."

"You think?" There was a smile in her voice. "So you would do it again?"

"Dear God, no."

"Okay - in a universe where we weren't actually related."

"Still no. But you're good. You lips taste - uh, what. I mean. Your mouth is good - um, uh - _ugh_. You get the idea."

He opened his eyes to see her expression. She looked fairly proud of herself. Jeez.

"Well, you know, you weren't too bad either. I would do it again, if you know what I mean." Rin winked and he swallowed thickly.

"I don't - but, er, thanks. Let's never do this again."

Her expression told him a different story. Oh dear. "Of course."

.

.

.

_seventeen_

Len had always been wrapped around Rin's finger ( _pretty tight_ if you must say), though he didn't really quite like admitting it. Even during the times they fought, rather than getting along, he was still ever ready to kiss her ass. Regrettably so. He didn't know why, but despite having pride and dignity, he was all too willing to drop it to run after her.

Consequently, he'd probably _literally_ kiss her ass someday. What she'd tricked him into doing over the past few years was certainly… not legal, or heading along that track, anyway. Kissing? Well, yeah, she was his first kiss. Then they did it _again_ , because she said, "I still need more practice!"

That kiss - well, it was, er, um…

Pretty intense. He had very little self-control.

So that made two kisses, for one. Besides that, he'd given her advice on all sorts of things that were certainly questionable, especially since it was advice from her _brother_ of all people; such as, uh, how to… _you know_ , please a guy. (Which was basically like, "You just rub his dick, Rin. Like, honestly. It isn't rocket science.") She'd tried to bribe him into giving her a demonstration, in which he screamed in response, " _Get out of my room!_ " So, thank goodness that hadn't turned out as bad as it could have.

Oh, what else was there…?

Well, there was _this_.

"Len," Rin began, appearing in his room one afternoon dressed in a skimpy dress that contrasted against her gorgeous, milky skin. Her hair was curled very slightly, and her face painted with a touch of makeup that accentuated her doe-like eyes. She looked like a doll.

He blinked at her for a few seconds, as if registering the sight. It wasn't often she dressed up like… _this_. "Uh, can I help you, Rin?"

She tucked a strand of hair behind her ear and carefully shut the door behind her, which made alarm bells go off in Len's head. _Oh great,_ he mused, _here we go._ "I need an opinion," she told him. "I'm going on a really nice anniversary date with my boyfriend and I really want to please him because I think we're going to…"

He tuned out instantly, already knowing the rest of the sentence. That's right - _boyfriend_. He forgot Rin had one. Well, no one could blame him - the guy was a bloody mystery. He'd never seen him before, let alone knew who he was, even. Sometimes he wondered if Rin even _had_ a boyfriend - but then again, it'd be super weird if she was asking him for advice… and to do _these things_ … when in reality it was for no reason.

Something told him that he shouldn't be surprised if the boyfriend was really a fake, though. It was typical of his sister to pull a prank as big as that.

"Len? Len, are you listening to me?"

Len blinked himself back to reality. Shit. Had he been staring at her for too long? His eyes met her face, and she tilted her head at him. "I was saying, I need your opinion on this."

He cleared his throat, scratching his head. "Yeah, yeah - it looks fine, Rin."

Rin's eyebrows furrowed. " _No_ ," she said, "I need your opinion on _this_ —" Her hands moved behind her, and for a second he thought she was going to brandish a knife and stab him. The thing was, he didn't even feel remotely scared, either - it was just another typical Rin move. Like, she would probably stab him if she had to. He just willingly accepted his death, then and there.

Instead of pulling out a knife from behind her, she pulled two strings loose and the entire dress came undone.

What the fuck.

It fell forward, fluttering down into a heap at her feet on the floor. Underneath, she had on a pair of matching, lacy lingerie - something he didn't even _know_ she had.

Len tore his eyes away from the sight, feeling his skin explode with an intense heat. An inhuman sound escaped from his throat - something between a _No_ and an _Oh_. Now, he did _not_ see that coming - but thank _God_ she's wearing _something_ underneath her clothes. He would've died and gone straight down to the bottom of the fiery pits of hell if she had been going all free-the-nipple.

Sweet mother of fuck, though.

"Well?" Rin asked.

He held up a hand in front of his eyes, worried he'll just keep _looking_. "Um. Very nice, Rin. Can you put your clothes back on, now?"

"No, no - what do you _think?_ What do you think of it? Do you like it?"

He parted his fingers slightly to catch a quick glimpse of her body, before snapping them shut again. He swallowed. "Very… um, frilly. Pretty." He was _not_ going to answer that last question.

She was silent for a moment. "So, do you think my boyfriend will like it?"

"Sure, Rin. He'll love it, I'm certain. His boner will knock him out—" Christ, "—um, yeah. Uh."

"Like yours is gonna do?"

"I'm _sorry?_ " He took his hand away from his face to glare at her, only to be met by the frills and _oh god_ , and _why_ and _how_ did she have such a great body? That was _not_ something he needed to know.

Rin's eyes glanced down at his crotch, a slight smirk fighting its way onto her face. He swallowed, moving his arms over his legs. "I saw it," she pointed out.

"Yeah, well, _why_ were you looking at my dick, anyway?" he demanded. "I - I wasn't anticipating you to _throw off_ your clothes, Rin. How else was I supposed to react? Jeez." He could feel himself turning redder and redder by the minute.

And he really wished she would put her clothes back on already. His eyes kept going places he didn't want them to go.

"Same reason why you keep talking to my boobs, you sick child," she responded, flicking her hair over her shoulder. "Well, anyway. Thanks for your help. If I can turn my brother on I bet I could turn anyone on." She winked at him, before pulling the dress on in one swift movement and leaving his room.

Len sunk down in his chair, urging the ceiling to suddenly cave in and crush his body.

Little Drummer Boy? More like Little Sinner Boy, if anything.

.

.

.

_eighteen_

It started with, "I need you to tell me if this lip gloss tastes nice."

Somehow it ended with Rin's lips on his, his tongue in her mouth, and her legs straddling his hips. The excuses were getting pretty poor in quality, honestly. But even the gods knew Len couldn't say no - or, well, fight back when his sister threw herself on him.

Rin moved away from his mouth to leave a trail of pecks down his neck. She stopped at his collarbone and rested her chin in the crook, hugging him tight.

There was reality tickling the edges of his mind, reminding him of who they were and what they were doing. But his demon pushed the thoughts aside, locked them away. _Just this once_ , it told his conscience, _just this once let me enjoy this_ —

"Hey, Len?" came his sister's small voice.

"Y-yeah?" His own voice was hoarse, stuck in his throat.

She pulled away to look at him, a rare solemn expression on her face. "Um, can I tell you something?" He nodded. She shifted nervously, eyes averting. "But you have to promise to not get angry at me."

Gee, it must be pretty serious if she had to say that. What, did she kill someone or something? Len licked his lips. "...Okay." He wasn't sure whether he could actually _promise_ that. It depended on what she was asking to promise about.

"I…" she started, then hesitated. She tucked a strand of hair behind her ear and looked up at him from under her lashes, trying out her puppy-dog face. "You know my boyfriend?"

"Yeah." He had a bad feeling about this.

"Well, um, he…" She took a breath. "He isn't real. I don't have a boyfriend. I never had."

Len blinked, processing what she'd just laid on him. "Um… _what?_ "

Rin laughed nervously to herself. "I don't have a boyfriend. All of this… you know, the practice runs and advice, uh, it was all a lie. There's no guy I'm dating or off having lustful sex with. Er, I'm - I, uh, in fact, have never had sex." The way she relayed this to him sounded as if she was proud of it, or something.

He stared at her, wondering why she was acting so excited to tell him she had been faking a relationship for the last two years and tricking him into, you know, _doing_ things. Bad things. With _her_. His sister.

"What the fuck," he muttered aloud, and Rin's smile faltered slightly. He lifted her up off his lap and stood, pressing his hands to his face. "You're telling me… this was all some kind of sick _joke?_ " Was her friends in on it? Who else knew that they'd kissed and all that?

His sister stood, walking towards him. "It's not a joke. Well, the boyfriend part _is_ , but like… I…" She took in his expression and stopped in her tracks. "You promised me you wouldn't get angry."

"Well, how would I know what I was promising to?" he asked. He rubbed his temples, furious. "So we… We practically made out, and straddled, and all that stuff - for _what?_ A source of entertainment to see me humiliated beyond relief? I… don't get you, Rin. Why would you do that? Why would you _lie_ to me?"

Rin's eyebrows furrowed and her bottom lip trembled. She looked like a kid again. "Why would I _lie_ to you?" she repeated slowly. "Why? Because, Len, what else was I supposed to say? Kiss me because I'm in love with you - even though we're twins?"

Len's eyes darkened. He couldn't believe what he was hearing. "You're in _love_ with me?"

"Yes," she answered firmly. "Yes, I am. I'm in love with you. I've been in love with you since we were kids. And I _knew_ you would respond like this, I _knew it_ \- that's why I tricked you. Because you wouldn't agree to anything if you knew I was in love with you."

He remained silent, seething. He wanted to yell at her, but even with the brave front she held, he knew she could easily shatter. He was angry at her, maybe a little disgusted, but he didn't want to break her.

Rin took his silence to keep speaking. "You know, I was hoping…" she trailed off. "I was hoping somehow that you would love me back, because you agreed to it all, and, you know - it just made sense. I was hoping you felt the same way too, so that's why I told you…"

His mouth remained shut. He knew if he spoke he would only say things, horrible things. Most of all, he felt betrayed - he felt like he lost all trust in her. There was a small voice in his head saying, _but think of her. Think of how she feels. She's in love with her brother - how terrifying would that be?_ It kept him grounded, stopped him from doing something he would regret later.

Once she got the message that he wasn't going to talk, she wrapped her arms around herself and said quietly, "I'm really sorry, Len. I am. I'm so sorry."

Then she left.

.

.

.

_nineteen_

They did not talk for a very long time. They moved out of home and started university and went down different paths.

Len tried to forget what had happened, what she'd said - but the more time went on with it unresolved, the more it drove him to insanity.

Rin _was_ important to him. She mattered. They'd relied on each other for so long now; this distance and lack of communication was overwhelming, almost. It was the worry-plagued thoughts that kept him awake at night, wondering where she was or what she was doing. The only way he knew she was doing well was the occasional updates on Facebook, or news from his parents.

He knew he could very well pick up the phone and call her and fix the broken links, but he didn't have the heart.

Then came New Years, and he had to return home to celebrate with family - and most of all, see Rin again.

"So, Len, I haven't heard much out of you," his mother said over dinner on the first night back. Rin sat across from him, staring down at her meal like it was the most intriguing thing on the planet. "How's study going? Have you made friends, met any girls?"

He cleared his throat awkwardly, not wanting to have to debrief his love life in front of his sister. "Um, uh, it's going okay. I made a few friends, yeah - and I was seeing this girl for a while, but it didn't really work out."

"Oh, I see. Rin here has been doing well in her studies, too - but goodness, no sort of romance in her life. Right, Rin?" Lily smirked over at her daughter, who seemed to shrink into her chair. "Gosh, when are you two going to give me grandchildren?"

"Well, we're only nineteen, Mum," Len defended.

"Kids are gross. They smell like poop and regrets," Rin added glumly. It was the first time he'd heard her talk that night.

"Imagine how _I_ felt when two of you came out," their mother scoffed. "We were only aiming for one - but _no_. It was like a miracle - a bad one."

They'd had this conversation multiple times before, but even so, Lily still had to bring up the topic that 'one of them was planned, and the other wasn't'. Len remembered fighting with Rin about it a long time ago, about who was the original baby, but it was a ridiculous argument where no one could win. So.

As if Rin remembered this memory, too, their eyes met over the dinner table - then they both averted their gazes quickly. Len sighed to himself internally. He felt like he had some major relationship rehashing to do.

Once dinner finished and he helped clean up in the kitchen, he went to fetch his pyjamas to have a shower. Unfortunately, it seemed Rin had beaten him to it - the door was locked and he could hear running water. Gee, the girl was fast. Perhaps she had planned to get in there first

He hung around in his room until she emerged from the bathroom, then stepped out into the hallway, meeting her halfway. She seemed to pause in front of him, a little like a cowering puppy, as if waiting for him to shout at her.

Her usually light blonde hair was dark, stuck to her skin in wet tendrils. She was much shorter than last time - er, perhaps he had grown a little. She had a towel wrapped around her, exposing white, creamy shoulders.

Len gave her a uncertain, small smile, drawing his eyes away from her skin. Here he was, cutting her off for what she'd done, but still had the guts to ogle at her - he was starting to sound like a hypocrite. Jeez.

"Did you leave any hot water for me?" he asked, trying to lighten the tension.

Rin seemed to hesitate, hugging her towel closer to her. "Of course not. Why would I leave hot water for someone as cold-hearted as you?"

"Ouch." He didn't know whether she was joking or not.

A small grin tugged at the corners of her lips. "Well, let me know what it's like freezing your dick off," she added, before disappearing into her bedroom.

Hmm. Well, it would certainly not be pleasant.

After his (thankfully hot) shower he decided he should sum up the courage to approach Rin and talk what happened through with her better. He wasn't sure how to even go about it, though - he wasn't sure whether it'd _fix_ anything, either, or just make it worse.

He knocked on her door and awaited a response. Eventually she opened the door and stopped on seeing him.

Her eyes flickered across his body. "Can I help you, Len?"

"Gee, I never thought you'd ask," he replied. She didn't budge. He raised his eyebrow. "Am I allowed to come in, or are you just going to make me stand out in the cold hallway?"

"What's the secret password?" she then inquired.

"Uh. What."

Rin mirrored his expression, raising an eyebrow. She folded her arms over her chest and leant against the doorway. "Secret password," she reiterated, stretching out each syllable as if talking to an incoherent child.

"I don't know. Sex? Password? Penis?"

She rolled her eyes. "Not even close."

"Aw, come on. I can't read minds."

"Well, I know _that_. Just use your manners. Gosh."

He sighed. "What, _please?_ "

Rin moved away to let him into her room, and he blinked, surprised. _Wow_ , he actually succeeded. He thought she'd be a pain and never let him in, and he'd have to make some ridiculous sacrifice.

She shut the door behind him. "So… you want to talk," she said, stepping past him to sit down on her bed.

"Well, yeah."

She looked at him expectantly.

Len swallowed. _Where do I even begin?_ he queried mentally.

He took a steady breath, preparing himself for the oncoming mental slaughter. "I'm sorry for… you know, distancing myself and leading you on and not really being very understanding about your feelings," he began. "I'm really, really sorry about it. I just - I was incredibly shocked about it all, you know? It was like one bombshell after the other. I was scared, most of all - about us, what we did. I was scared of your feelings, my feelings, about other people finding out. Most of all, I just felt hurt because I trusted you to be honest with me. But I guess I can see why you weren't. It was a lose-lose situation, either way."

Rin sat still, eyes on the floor, thinking. Her fingers traced circles in the duvet on her bed. "No… I guess I should've known better, though. It was my fault as well, Len."

He watched her, curious. "You know, I… I don't want us to grow apart," he told her. "I just can't stop thinking about y—" He stopped himself mid-sentence, realising what he was about to say. His cheeks instantly grew warm. Well, fuck. That sounded totally creepy.

It was too late to take it back - a smirk fixed across his sister's lips. "Can't stop, huh? No wonder your relationship didn't last."

"What? There… there were other reasons, okay? What I meant was… I worried about you. Everyday. I felt guilty about how I cut you off. I didn't want to lose you, because you're still important to me, Rin."

Rin exhaled, closing her eyes. "What I want to know is why you seemed to… eventually fall so easy for my tricks. I knew you knew what I was doing, but you seemed to just become more willing to do anything as time went on. That day I confessed to you, I was so sure that you loved me. The way you kissed me back was… like you felt the same way as I did, too."

Len gazed at her, a guilty pang in his chest. There was a jumble of words in his mouth, and he wasn't sure how to string them out in a way that was coherent.

"I don't know how I feel," he admitted slowly. He pressed his lips together, thinking long and hard. "I liked it, I guess. I liked kissing you. At the same time I knew it was wrong - I didn't want to enjoy it. But I did. I just tried so hard to ignore it. I don't know whether I'm in love with you. I can't say it. I know for sure I _love_ you, as my sister, and I would do anything _for_ you because you mean a lot to me. But it still doesn't make sense - because I loved to kiss you. I loved to hold you. I loved doing things with you that a brother never should."

She opened her eyes again. "It's like that, isn't it," she murmured. "A constant pushing and pulling of what's right and what's wrong. You know you shouldn't do it, you shouldn't _feel_ this way, but… you do and there's nothing you can do about it. You can either give in to it, or fight against it your whole life."

Rin's eyes flickered up to his face, held his gaze there. "Are you going to fight against it?"

Suddenly, the room's walls felt like they were closing around him and there was no escape. He'd always felt like he'd been too reliant on her, chasing after her always - but had she really been the one who'd followed after him and looked to him?

_I've been in love with you since we were kids._

"I don't know," he mumbled.

_I want to kiss you. I want to hold you. I want to forget everything bad but I also just want to push you away and forget how I feel. I love you but I don't, I don't want to_.

Rin stood and approached him, pulling him into a tight embrace. "You can do whatever you want to do," she whispered against his chest. "But please don't ever _hate_ me. That hurts the most."

Len drew a hand down her back, feeling the shape of her spine through her shirt. Warmth, and she smelt so sweet and familiar and Rin - he'd missed the scent. He'd missed holding her tiny body in his arms. Most of all, he'd missed her.

She stepped away, looking up at him again.

_Damn it, damn it, damn it._ His heart swelled in his chest and he just couldn't take it anymore. She just had him wrapped so tight around her little finger.

He cupped her face in his hands and pressed his lips gently against hers. Then he broke away to say, "We can't."

Rin pulled him back down to her lips, kissing him again, before asking, "We can't what?"

"We can't," he murmured against her mouth, "let anyone know about this."

She gazed up into his eyes. "I know," she whispered. "I know, and no one will. I promise, Len." She pulled down his hands from her face to hold them in her own, steering him towards her bed. She gently pushed him down onto the mattress, sliding her legs over his. "You know I love you too much to ever want to lose you."

.

.

.

_twenty-one_

The sound of a vibrating phone broke them apart, and Rin reached past Len's head to answer it.

"Who is it?" he mouthed, shifting under her weight.

She sat up, earning a strained _oomf_ from him. "Mum," she hissed in response, before holding the phone up to her ear. "Hey Mummy?"

Len let his head fall back against the pillow. This wasn't the first time they were interrupted by a family member - not the last, he guessed, either. It was probably a sign from the gods telling them to stop, but _as if_ they'd ever listen.

Rin frowned at whatever her mother was relaying to her through the phone. "I'm hanging out with Len today," she told her. "Yeah. We're just having lunch and watching a movie at his place."

She was absentmindedly stroking his stomach, fingertips grazing ever so slightly over the surface of his skin, drawing circles and hearts and whatnot. He squirmed under her, impatient to continue what they were just about to do—

"Oh shush! What's wrong with wanting to spend quality time with my awesome brother?" Just as she was saying that, she glanced down at him and gave him a wink. Len rolled his eyes. "Look, he's getting impatient, I tell you. We were just up to the climax - can I call you later, Mummy?"

He held in a groan. _He_ was also on his way to the climax, dammit.

Rin moved against his groin and he let out a small whimper. The girl was evil. "Okay, I'll talk later. Bye-bye." She hung up the phone, tossing it aside. She leant back down onto him. "Now, where _were_ we?"

"What did she want to talk about?" Len asked as she pressed her lips against his neck.

"Oh, just wanted to tease me about my lack of relationships. Did you tell her you had a girlfriend, or something?" his sister questioned.

"Er, maybe. I hinted it. Just so she could get off my back," he murmured, voice hitching as her hand slipped down his pants.

Rin sighed, hot breath hitting his chest. "Gee, thanks. Well she'll be disappointed when you have yet another failed relationship with no kids. What are we gonna do about that? She'll be even more annoying than she already is."

"We could just adopt some."

"Us? _Siblings? Adopt kids?_ No way. They'd be calling child services quick smart if anyone found out we were actually adopting… for _us_."

Len grunted. "Well, I don't know, then."

His sister tossed her shirt aside and moved in to kiss him on the lips, all too sweet. "Whatever. We'll figure it out. We always do."

**#justsiblingthings**

**Author's Note:**

> edit: removed anything to do with the receiver of this fic bc she didnt like it, very obviously did not like it, and i guess it doesnt matter that i wasted my time trying to be nice or anything now so like, never mind, lets pretend i wrote this for no one and it'll hurt a little less :)
> 
> i have returned with yet another sin. take it. merry christmas.
> 
> i gtg spray holy water into me eyes
> 
> (this was literally plotness im sorry idc guilty pleasures are mINE)


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